This invention relates to method and systems for lining shafts such as mining shafts, and more particularly relates to a system utilizing precast liner panels.
Shafts or tunnels bored into the earth are used for a variety of purposes. For example, mining shafts are used for the production and transportation of men and materials or mine ventilation from the surface. Internal raises or winzes are used for the passage of water, waste, or men and materials within a mine. Construction shafts are also used for ventilation in transportation tunnels, water passageways, etc., and may be vertical or inclined. These tunnels or shafts are conventionally constructed by drilling, blasting, mucking or by drilling (boring).
Most of the shafts constructed today are circular in cross-section and lined with concrete. The concrete lining provides protection from weathering for the wall rock. The smooth passage for ventilation air also provides structural integrity for the tunnel and permits ground water control.
In the present system of constructing and lining shafts, the placement of concrete is time-consuming and expensive as it normally interrupts the construction of the shaft. Various types of wood and metal forms are lowered into place below the last-lined portion of the shaft and braced into place and concrete filled in behind the forms between the forms and the wall rock. Frequently much time is lost waiting for the concrete to cure and strengthen before the forms may be stripped and removed out of the way. Drilling and construction may then proceed with subsequent sections lined with concrete by again placing the forms and filling with concrete. As can be perceived, this can be extremely time-consuming and expensive.
With the present invention, it is proposed that the wooden or metal forms be replaced by precast concrete liner panels which will be manufactured or fabricated at the surface and left in place in the tunnel or shaft after grouting. The thickness and dimensions of the precast concrete lining panels will, of course, be dictated by the particular local conditions under which the tunnel or shaft is being constructed. The precast liner for each vertical liner section will be in a plurality of panels, usually three or more. In special cases when the precast liner has a width less than half its length, each vertical liner section may be composed of two panels. This facilitates passing liner panels through the already previously lined sections.
After each section is assembled in place, temporarily secured and set in place by filling in the void behind the cast sections, a new section can be started. The new section is produced by passing liner panels down through the previous section and assembling them. The new sections can be hung from hangers on inserts precast in the bottom edge of the previous liner panels, if desired. After blocking or temporarily securing the assembled liner panels in place, the void or gap between the bottom of the lining and the wall rock will be plugged. This may be accomplished by utilizing an inflatable donut-shaped ring which may be activated by compressed air. This would conform and fill to the irregularities of the wall rock and allow pouring of the curb ring at the bottom of the liner section. Preferably the curb ring would be poured with a fast-setting concrete as it merely serves the purpose of acting as a stop during pouring and filling of the void behind the liner section. After the curb ring has gained sufficient strength, the balance of the void behind the liner section can then be filled with concrete. The inflatable ring may then be deflated and removed when the curb ring has set sufficiently. The filler concrete, which is mixed on the surface, may be passed through a pipe, and remix kettle, if required, to fill the void between the lining and the wall rock. The pipe is inserted in an aperture or grouting door precast into the liner panels. One or more sections could be placed at a given time, if desired, depending upon the particular job requirements, size, shape and length of the shaft.
As was described, grouting may be accomplished through grout doors in each new liner section or through a grout ring at the bottom of the previous grouted section or through grout valves in the lining panel.
To insure a good bond between the liner panels and the grout, the surface of the liner panels facing the shaft wall could be cast with an irregular surface or embedments may be placed in the lining which protrude into the grout area, providing a gripping surface. Pipe hangers or other shaft fittings may be cast in place in the liner panels, if desired. Water rings also can be cast into selected liner panel sections.
Joints or connections between the adjacent liner sections, both vertically and horizontally, and between respective liner panels in each liner section can be provided by casting a joint into the edges of the liner panels, such as a modified tongue-in-groove so that the fit of each liner panel may be checked on the surface before placement in the shaft or tunnel. If the particular environment is such that ground water is a problem, packing may be introduced into the tongue-in-groove area, if so desired. Each new liner section may be put into place from a special platform positioned in the shaft or may be assembled together at the bottom of the shaft and hoisted into place up against the previous liner section. The hangers precast at the bottom edge of the liner panels for connecting the new section to the previous section can be fitted with bolts, or other quick-tightening mechanisms to effect a tight closure. The hangers can later be used for shaft fittings or cut away if not found useful.
The use of precast liner panels fitted against the walls of the shaft interlocking with one another can be adapted for use in either square, rectangular, oblong, or any other shape and combination shapes for shafts. Use of the precast liner panels for lining shafts effectively saves time and money by permitting quick and easy placement and setting of liner sections allowing more time for the actual construction or boring of the shaft.
Thus, the principal object of the present invention is to provide a method and system for quickly and efficiently lining shafts with precast liner panels fitted and set into place in the shaft.
Other objects, advantages and novel features of the invention will become apparent from the following detailed description and the accompanying drawings, wherein like reference numbers identify like parts throughout.